The practical use of photovoltaic systems, which convert incident sunlight into electrical energy, continues to be of significant interest to the power generation industry. The development of more efficient solar cells, as well as the lower production costs realized by the manufacture of continuously deposited, amorphous solar cells, has made photovoltaic systems more realizable. Photovoltaic modules are being commercially used today to power devices such as radios, to trickle charge batteries in parked cars, and in night illumination systems.
Photovoltaic arrays may be used in a wide variety of additional settings. In general, photovoltaics may be used remotely with specific loads (e.g., signal repeating towers) or with unspecific loads (e.g., off-grid residences, off-grid villages), or connected to a power supply grid. Further, a photovoltaics supply may be connected to a power grid either on the customer-side or on the utility-side of an electric meter, depending upon who owns the system. The present invention is directed principally to applications concerning function-unspecific loads, primarily, but not uniquely in the context of grid-connected systems and on either side of the meter.
High efficiency power conditioning units (PCUs) are commercially available today to ensure that photovoltaic arrays operate near their maximum power point. These PCUs maximize energy transfer from sunlight to usable AC electricity. Under actual conditions, a 1 kW rated array is typically capable of producing anywhere between 1300 and 2500 kWh per year in the United States depending on local climate and array geometry. By contrast, an ideal generator working twenty-four hours per day would produce 8760 kWh per year per rated kW. The ratio between the photovoltaic array output and this ideal output is referred to as capacity factor. Hence, for a photovoltaic array, the capacity factor typically ranges from 15% to 28%. Electrical power plants derive value not only from energy production (their capacity factor) but also from their capacity, that is their contribution to a utility's spinning reserve, hence their ability to deliver power on demand.
Overall, the capacity value of an ideally dispatchable power plant is of the same order as the value of the energy delivered by that plant. Hence, the economics of photovoltaics have traditionally been penalized by the fact that no capacity value is considered for this resource. The present invention is thus directed to capturing additional value for photovoltaics (as well as other non-controllable, renewable resources) by increasing or even maximizing effective capacity of the non-controllable power supply when coupled to a power grid.